/*-------------------------------------------------------------------------
 *
 * execExpr.c
 *      Expression evaluation infrastructure.
 *
 *    During executor startup, we compile each expression tree (which has
 *    previously been processed by the parser and planner) into an ExprState,
 *    using ExecInitExpr() et al.  This converts the tree into a flat array
 *    of ExprEvalSteps, which may be thought of as instructions in a program.
 *    At runtime, we'll execute steps, starting with the first, until we reach
 *    an EEOP_DONE opcode.
 *
 *    This file contains the "compilation" logic.  It is independent of the
 *    specific execution technology we use (switch statement, computed goto,
 *    JIT compilation, etc).
 *
 *    See src/backend/executor/README for some background, specifically the
 *    "Expression Trees and ExprState nodes", "Expression Initialization",
 *    and "Expression Evaluation" sections.
 *
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      src/backend/executor/execExpr.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/nbtree.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_type.h"
#include "executor/execExpr.h"
#include "executor/nodeSubplan.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/planner.h"
#include "pgstat.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/typcache.h"


typedef struct LastAttnumInfo
{
    AttrNumber    last_inner;
    AttrNumber    last_outer;
    AttrNumber    last_scan;
} LastAttnumInfo;

static void ExecReadyExpr(ExprState *state);
static void ExecInitExprRec(Expr *node, PlanState *parent, ExprState *state,
                Datum *resv, bool *resnull);
static void ExprEvalPushStep(ExprState *es, const ExprEvalStep *s);
static void ExecInitFunc(ExprEvalStep *scratch, Expr *node, List *args,
             Oid funcid, Oid inputcollid, PlanState *parent,
             ExprState *state);
static void ExecInitExprSlots(ExprState *state, Node *node);
static bool get_last_attnums_walker(Node *node, LastAttnumInfo *info);
static void ExecInitWholeRowVar(ExprEvalStep *scratch, Var *variable,
                    PlanState *parent);
static void ExecInitArrayRef(ExprEvalStep *scratch, ArrayRef *aref,
                 PlanState *parent, ExprState *state,
                 Datum *resv, bool *resnull);
static bool isAssignmentIndirectionExpr(Expr *expr);
static void ExecInitCoerceToDomain(ExprEvalStep *scratch, CoerceToDomain *ctest,
                       PlanState *parent, ExprState *state,
                       Datum *resv, bool *resnull);


/*
 * ExecInitExpr: prepare an expression tree for execution
 *
 * This function builds and returns an ExprState implementing the given
 * Expr node tree.  The return ExprState can then be handed to ExecEvalExpr
 * for execution.  Because the Expr tree itself is read-only as far as
 * ExecInitExpr and ExecEvalExpr are concerned, several different executions
 * of the same plan tree can occur concurrently.  (But note that an ExprState
 * does mutate at runtime, so it can't be re-used concurrently.)
 *
 * This must be called in a memory context that will last as long as repeated
 * executions of the expression are needed.  Typically the context will be
 * the same as the per-query context of the associated ExprContext.
 *
 * Any Aggref, WindowFunc, or SubPlan nodes found in the tree are added to
 * the lists of such nodes held by the parent PlanState (or more accurately,
 * the AggrefExprState etc. nodes created for them are added).
 *
 * Note: there is no ExecEndExpr function; we assume that any resource
 * cleanup needed will be handled by just releasing the memory context
 * in which the state tree is built.  Functions that require additional
 * cleanup work can register a shutdown callback in the ExprContext.
 *
 *    'node' is the root of the expression tree to compile.
 *    'parent' is the PlanState node that owns the expression.
 *
 * 'parent' may be NULL if we are preparing an expression that is not
 * associated with a plan tree.  (If so, it can't have aggs or subplans.)
 * Such cases should usually come through ExecPrepareExpr, not directly here.
 *
 * Also, if 'node' is NULL, we just return NULL.  This is convenient for some
 * callers that may or may not have an expression that needs to be compiled.
 * Note that a NULL ExprState pointer *cannot* be handed to ExecEvalExpr,
 * although ExecQual and ExecCheck will accept one (and treat it as "true").
 */
ExprState *
ExecInitExpr(Expr *node, PlanState *parent)
{
    ExprState  *state;
    ExprEvalStep scratch;

    /* Special case: NULL expression produces a NULL ExprState pointer */
    if (node == NULL)
        return NULL;

    /* Initialize ExprState with empty step list */
    state = makeNode(ExprState);
    state->expr = node;

    /* Insert EEOP_*_FETCHSOME steps as needed */
    ExecInitExprSlots(state, (Node *) node);

    /* Compile the expression proper */
    ExecInitExprRec(node, parent, state, &state->resvalue, &state->resnull);

    /* Finally, append a DONE step */
    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return state;
}

/*
 * ExecInitQual: prepare a qual for execution by ExecQual
 *
 * Prepares for the evaluation of a conjunctive boolean expression (qual list
 * with implicit AND semantics) that returns true if none of the
 * subexpressions are false.
 *
 * We must return true if the list is empty.  Since that's a very common case,
 * we optimize it a bit further by translating to a NULL ExprState pointer
 * rather than setting up an ExprState that computes constant TRUE.  (Some
 * especially hot-spot callers of ExecQual detect this and avoid calling
 * ExecQual at all.)
 *
 * If any of the subexpressions yield NULL, then the result of the conjunction
 * is false.  This makes ExecQual primarily useful for evaluating WHERE
 * clauses, since SQL specifies that tuples with null WHERE results do not
 * get selected.
 */
ExprState *
ExecInitQual(List *qual, PlanState *parent)
{
    ExprState  *state;
    ExprEvalStep scratch;
    List       *adjust_jumps = NIL;
    ListCell   *lc;

    /* short-circuit (here and in ExecQual) for empty restriction list */
    if (qual == NIL)
        return NULL;

    Assert(IsA(qual, List));

    state = makeNode(ExprState);
    state->expr = (Expr *) qual;
    /* mark expression as to be used with ExecQual() */
    state->flags = EEO_FLAG_IS_QUAL;

    /* Insert EEOP_*_FETCHSOME steps as needed */
    ExecInitExprSlots(state, (Node *) qual);

    /*
     * ExecQual() needs to return false for an expression returning NULL. That
     * allows us to short-circuit the evaluation the first time a NULL is
     * encountered.  As qual evaluation is a hot-path this warrants using a
     * special opcode for qual evaluation that's simpler than BOOL_AND (which
     * has more complex NULL handling).
     */
    scratch.opcode = EEOP_QUAL;

    /*
     * We can use ExprState's resvalue/resnull as target for each qual expr.
     */
    scratch.resvalue = &state->resvalue;
    scratch.resnull = &state->resnull;

    foreach(lc, qual)
    {
        Expr       *node = (Expr *) lfirst(lc);

        /* first evaluate expression */
        ExecInitExprRec(node, parent, state, &state->resvalue, &state->resnull);

        /* then emit EEOP_QUAL to detect if it's false (or null) */
        scratch.d.qualexpr.jumpdone = -1;
        ExprEvalPushStep(state, &scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
    }

    /* adjust jump targets */
    foreach(lc, adjust_jumps)
    {
        ExprEvalStep *as = &state->steps[lfirst_int(lc)];

        Assert(as->opcode == EEOP_QUAL);
        Assert(as->d.qualexpr.jumpdone == -1);
        as->d.qualexpr.jumpdone = state->steps_len;
    }

    /*
     * At the end, we don't need to do anything more.  The last qual expr must
     * have yielded TRUE, and since its result is stored in the desired output
     * location, we're done.
     */
    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return state;
}

/*
 * ExecInitCheck: prepare a check constraint for execution by ExecCheck
 *
 * This is much like ExecInitQual/ExecQual, except that a null result from
 * the conjunction is treated as TRUE.  This behavior is appropriate for
 * evaluating CHECK constraints, since SQL specifies that NULL constraint
 * conditions are not failures.
 *
 * Note that like ExecInitQual, this expects input in implicit-AND format.
 * Users of ExecCheck that have expressions in normal explicit-AND format
 * can just apply ExecInitExpr to produce suitable input for ExecCheck.
 */
ExprState *
ExecInitCheck(List *qual, PlanState *parent)
{
    /* short-circuit (here and in ExecCheck) for empty restriction list */
    if (qual == NIL)
        return NULL;

    Assert(IsA(qual, List));

    /*
     * Just convert the implicit-AND list to an explicit AND (if there's more
     * than one entry), and compile normally.  Unlike ExecQual, we can't
     * short-circuit on NULL results, so the regular AND behavior is needed.
     */
    return ExecInitExpr(make_ands_explicit(qual), parent);
}

/*
 * Call ExecInitExpr() on a list of expressions, return a list of ExprStates.
 */
List *
ExecInitExprList(List *nodes, PlanState *parent)
{
    List       *result = NIL;
    ListCell   *lc;

    foreach(lc, nodes)
    {
        Expr       *e = lfirst(lc);

        result = lappend(result, ExecInitExpr(e, parent));
    }

    return result;
}

/*
 *        ExecBuildProjectionInfo
 *
 * Build a ProjectionInfo node for evaluating the given tlist in the given
 * econtext, and storing the result into the tuple slot.  (Caller must have
 * ensured that tuple slot has a descriptor matching the tlist!)
 *
 * inputDesc can be NULL, but if it is not, we check to see whether simple
 * Vars in the tlist match the descriptor.  It is important to provide
 * inputDesc for relation-scan plan nodes, as a cross check that the relation
 * hasn't been changed since the plan was made.  At higher levels of a plan,
 * there is no need to recheck.
 *
 * This is implemented by internally building an ExprState that performs the
 * whole projection in one go.
 *
 * Caution: before PG v10, the targetList was a list of ExprStates; now it
 * should be the planner-created targetlist, since we do the compilation here.
 */
ProjectionInfo *
ExecBuildProjectionInfo(List *targetList,
                        ExprContext *econtext,
                        TupleTableSlot *slot,
                        PlanState *parent,
                        TupleDesc inputDesc)
{// #lizard forgives
    ProjectionInfo *projInfo = makeNode(ProjectionInfo);
    ExprState  *state;
    ExprEvalStep scratch;
    ListCell   *lc;

    projInfo->pi_exprContext = econtext;
    /* We embed ExprState into ProjectionInfo instead of doing extra palloc */
    projInfo->pi_state.tag.type = T_ExprState;
    state = &projInfo->pi_state;
    state->expr = (Expr *) targetList;
    state->resultslot = slot;

    /* Insert EEOP_*_FETCHSOME steps as needed */
    ExecInitExprSlots(state, (Node *) targetList);

    /* Now compile each tlist column */
    foreach(lc, targetList)
    {
        TargetEntry *tle = lfirst_node(TargetEntry, lc);
        Var           *variable = NULL;
        AttrNumber    attnum = 0;
        bool        isSafeVar = false;

        /*
         * If tlist expression is a safe non-system Var, use the fast-path
         * ASSIGN_*_VAR opcodes.  "Safe" means that we don't need to apply
         * CheckVarSlotCompatibility() during plan startup.  If a source slot
         * was provided, we make the equivalent tests here; if a slot was not
         * provided, we assume that no check is needed because we're dealing
         * with a non-relation-scan-level expression.
         */
        if (tle->expr != NULL &&
            IsA(tle->expr, Var) &&
            ((Var *) tle->expr)->varattno > 0)
        {
            /* Non-system Var, but how safe is it? */
            variable = (Var *) tle->expr;
            attnum = variable->varattno;

            if (inputDesc == NULL)
                isSafeVar = true;    /* can't check, just assume OK */
            else if (attnum <= inputDesc->natts)
            {
                Form_pg_attribute attr = inputDesc->attrs[attnum - 1];

                /*
                 * If user attribute is dropped or has a type mismatch, don't
                 * use ASSIGN_*_VAR.  Instead let the normal expression
                 * machinery handle it (which'll possibly error out).
                 */
                if (!attr->attisdropped && variable->vartype == attr->atttypid)
                {
                    isSafeVar = true;
                }
            }
        }

        if (isSafeVar)
        {
            /* Fast-path: just generate an EEOP_ASSIGN_*_VAR step */
            switch (variable->varno)
            {
                case INNER_VAR:
                    /* get the tuple from the inner node */
                    scratch.opcode = EEOP_ASSIGN_INNER_VAR;
                    break;

                case OUTER_VAR:
                    /* get the tuple from the outer node */
                    scratch.opcode = EEOP_ASSIGN_OUTER_VAR;
                    break;

                    /* INDEX_VAR is handled by default case */

                default:
                    /* get the tuple from the relation being scanned */
                    scratch.opcode = EEOP_ASSIGN_SCAN_VAR;
                    break;
            }

            scratch.d.assign_var.attnum = attnum - 1;
            scratch.d.assign_var.resultnum = tle->resno - 1;
            ExprEvalPushStep(state, &scratch);
        }
        else
        {
            /*
             * Otherwise, compile the column expression normally.
             *
             * We can't tell the expression to evaluate directly into the
             * result slot, as the result slot (and the exprstate for that
             * matter) can change between executions.  We instead evaluate
             * into the ExprState's resvalue/resnull and then move.
             */
            ExecInitExprRec(tle->expr, parent, state,
                            &state->resvalue, &state->resnull);

            /*
             * Column might be referenced multiple times in upper nodes, so
             * force value to R/O - but only if it could be an expanded datum.
             */
            if (get_typlen(exprType((Node *) tle->expr)) == -1)
                scratch.opcode = EEOP_ASSIGN_TMP_MAKE_RO;
            else
                scratch.opcode = EEOP_ASSIGN_TMP;
            scratch.d.assign_tmp.resultnum = tle->resno - 1;
            ExprEvalPushStep(state, &scratch);
        }
    }

    scratch.opcode = EEOP_DONE;
    ExprEvalPushStep(state, &scratch);

    ExecReadyExpr(state);

    return projInfo;
}

/*
 * ExecPrepareExpr --- initialize for expression execution outside a normal
 * Plan tree context.
 *
 * This differs from ExecInitExpr in that we don't assume the caller is
 * already running in the EState's per-query context.  Also, we run the
 * passed expression tree through expression_planner() to prepare it for
 * execution.  (In ordinary Plan trees the regular planning process will have
 * made the appropriate transformations on expressions, but for standalone
 * expressions this won't have happened.)
 */
ExprState *
ExecPrepareExpr(Expr *node, EState *estate)
{
    ExprState  *result;
    MemoryContext oldcontext;

    oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

    node = expression_planner(node);

    result = ExecInitExpr(node, NULL);

    MemoryContextSwitchTo(oldcontext);

    return result;
}

/*
 * ExecPrepareQual --- initialize for qual execution outside a normal
 * Plan tree context.
 *
 * This differs from ExecInitQual in that we don't assume the caller is
 * already running in the EState's per-query context.  Also, we run the
 * passed expression tree through expression_planner() to prepare it for
 * execution.  (In ordinary Plan trees the regular planning process will have
 * made the appropriate transformations on expressions, but for standalone
 * expressions this won't have happened.)
 */
ExprState *
ExecPrepareQual(List *qual, EState *estate)
{
    ExprState  *result;
    MemoryContext oldcontext;

    oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

    qual = (List *) expression_planner((Expr *) qual);

    result = ExecInitQual(qual, NULL);

    MemoryContextSwitchTo(oldcontext);

    return result;
}

/*
 * ExecPrepareCheck -- initialize check constraint for execution outside a
 * normal Plan tree context.
 *
 * See ExecPrepareExpr() and ExecInitCheck() for details.
 */
ExprState *
ExecPrepareCheck(List *qual, EState *estate)
{
    ExprState  *result;
    MemoryContext oldcontext;

    oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

    qual = (List *) expression_planner((Expr *) qual);

    result = ExecInitCheck(qual, NULL);

    MemoryContextSwitchTo(oldcontext);

    return result;
}

/*
 * Call ExecPrepareExpr() on each member of a list of Exprs, and return
 * a list of ExprStates.
 *
 * See ExecPrepareExpr() for details.
 */
List *
ExecPrepareExprList(List *nodes, EState *estate)
{
    List       *result = NIL;
    MemoryContext oldcontext;
    ListCell   *lc;

    /* Ensure that the list cell nodes are in the right context too */
    oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

    foreach(lc, nodes)
    {
        Expr       *e = (Expr *) lfirst(lc);

        result = lappend(result, ExecPrepareExpr(e, estate));
    }

    MemoryContextSwitchTo(oldcontext);

    return result;
}

/*
 * ExecCheck - evaluate a check constraint
 *
 * For check constraints, a null result is taken as TRUE, ie the constraint
 * passes.
 *
 * The check constraint may have been prepared with ExecInitCheck
 * (possibly via ExecPrepareCheck) if the caller had it in implicit-AND
 * format, but a regular boolean expression prepared with ExecInitExpr or
 * ExecPrepareExpr works too.
 */
bool
ExecCheck(ExprState *state, ExprContext *econtext)
{
    Datum        ret;
    bool        isnull;

    /* short-circuit (here and in ExecInitCheck) for empty restriction list */
    if (state == NULL)
        return true;

    /* verify that expression was not compiled using ExecInitQual */
    Assert(!(state->flags & EEO_FLAG_IS_QUAL));

    ret = ExecEvalExprSwitchContext(state, econtext, &isnull);

    if (isnull)
        return true;

    return DatumGetBool(ret);
}

/*
 * Prepare a compiled expression for execution.  This has to be called for
 * every ExprState before it can be executed.
 *
 * NB: While this currently only calls ExecReadyInterpretedExpr(),
 * this will likely get extended to further expression evaluation methods.
 * Therefore this should be used instead of directly calling
 * ExecReadyInterpretedExpr().
 */
static void
ExecReadyExpr(ExprState *state)
{
    ExecReadyInterpretedExpr(state);
}

/*
 * Append the steps necessary for the evaluation of node to ExprState->steps,
 * possibly recursing into sub-expressions of node.
 *
 * node - expression to evaluate
 * parent - parent executor node (or NULL if a standalone expression)
 * state - ExprState to whose ->steps to append the necessary operations
 * resv / resnull - where to store the result of the node into
 */
static void
ExecInitExprRec(Expr *node, PlanState *parent, ExprState *state,
                Datum *resv, bool *resnull)
{// #lizard forgives
    ExprEvalStep scratch;

    /* Guard against stack overflow due to overly complex expressions */
    check_stack_depth();

    /* Step's output location is always what the caller gave us */
    Assert(resv != NULL && resnull != NULL);
    scratch.resvalue = resv;
    scratch.resnull = resnull;

    /* cases should be ordered as they are in enum NodeTag */
    switch (nodeTag(node))
    {
        case T_Var:
            {
                Var           *variable = (Var *) node;

                if (variable->varattno == InvalidAttrNumber)
                {
                    /* whole-row Var */
                    ExecInitWholeRowVar(&scratch, variable, parent);
                }
                else if (variable->varattno <= 0)
                {
                    /* system column */
                    scratch.d.var.attnum = variable->varattno;
                    scratch.d.var.vartype = variable->vartype;
                    switch (variable->varno)
                    {
                        case INNER_VAR:
                            scratch.opcode = EEOP_INNER_SYSVAR;
                            break;
                        case OUTER_VAR:
                            scratch.opcode = EEOP_OUTER_SYSVAR;
                            break;

                            /* INDEX_VAR is handled by default case */

                        default:
                            scratch.opcode = EEOP_SCAN_SYSVAR;
                            break;
                    }
                }
                else
                {
                    /* regular user column */
                    scratch.d.var.attnum = variable->varattno - 1;
                    scratch.d.var.vartype = variable->vartype;
                    /* select EEOP_*_FIRST opcode to force one-time checks */
                    switch (variable->varno)
                    {
                        case INNER_VAR:
                            scratch.opcode = EEOP_INNER_VAR_FIRST;
                            break;
                        case OUTER_VAR:
                            scratch.opcode = EEOP_OUTER_VAR_FIRST;
                            break;

                            /* INDEX_VAR is handled by default case */

                        default:
                            scratch.opcode = EEOP_SCAN_VAR_FIRST;
                            break;
                    }
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_Const:
            {
                Const       *con = (Const *) node;

                scratch.opcode = EEOP_CONST;
                scratch.d.constval.value = con->constvalue;
                scratch.d.constval.isnull = con->constisnull;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_Param:
            {
                Param       *param = (Param *) node;

                switch (param->paramkind)
                {
                    case PARAM_EXEC:
                        scratch.opcode = EEOP_PARAM_EXEC;
                        scratch.d.param.paramid = param->paramid;
                        scratch.d.param.paramtype = param->paramtype;
                        break;
                    case PARAM_EXTERN:
                        scratch.opcode = EEOP_PARAM_EXTERN;
                        scratch.d.param.paramid = param->paramid;
                        scratch.d.param.paramtype = param->paramtype;
                        break;
                    default:
                        elog(ERROR, "unrecognized paramkind: %d",
                             (int) param->paramkind);
                        break;
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_Aggref:
            {
                Aggref       *aggref = (Aggref *) node;
                AggrefExprState *astate = makeNode(AggrefExprState);

                scratch.opcode = EEOP_AGGREF;
                scratch.d.aggref.astate = astate;
                astate->aggref = aggref;

                if (parent && IsA(parent, AggState))
                {
                    AggState   *aggstate = (AggState *) parent;

                    aggstate->aggs = lcons(astate, aggstate->aggs);
                    aggstate->numaggs++;
                }
                else
                {
                    /* planner messed up */
                    elog(ERROR, "Aggref found in non-Agg plan node");
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_GroupingFunc:
            {
                GroupingFunc *grp_node = (GroupingFunc *) node;
                Agg           *agg;

                if (!parent || !IsA(parent, AggState) ||
                    !IsA(parent->plan, Agg))
                    elog(ERROR, "GroupingFunc found in non-Agg plan node");

                scratch.opcode = EEOP_GROUPING_FUNC;
                scratch.d.grouping_func.parent = (AggState *) parent;

                agg = (Agg *) (parent->plan);

                if (agg->groupingSets)
                    scratch.d.grouping_func.clauses = grp_node->cols;
                else
                    scratch.d.grouping_func.clauses = NIL;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_WindowFunc:
            {
                WindowFunc *wfunc = (WindowFunc *) node;
                WindowFuncExprState *wfstate = makeNode(WindowFuncExprState);

                wfstate->wfunc = wfunc;

                if (parent && IsA(parent, WindowAggState))
                {
                    WindowAggState *winstate = (WindowAggState *) parent;
                    int            nfuncs;

                    winstate->funcs = lcons(wfstate, winstate->funcs);
                    nfuncs = ++winstate->numfuncs;
                    if (wfunc->winagg)
                        winstate->numaggs++;

                    /* for now initialize agg using old style expressions */
                    wfstate->args = ExecInitExprList(wfunc->args, parent);
                    wfstate->aggfilter = ExecInitExpr(wfunc->aggfilter,
                                                      parent);

                    /*
                     * Complain if the windowfunc's arguments contain any
                     * windowfuncs; nested window functions are semantically
                     * nonsensical.  (This should have been caught earlier,
                     * but we defend against it here anyway.)
                     */
                    if (nfuncs != winstate->numfuncs)
                        ereport(ERROR,
                                (errcode(ERRCODE_WINDOWING_ERROR),
                                 errmsg("window function calls cannot be nested")));
                }
                else
                {
                    /* planner messed up */
                    elog(ERROR, "WindowFunc found in non-WindowAgg plan node");
                }

                scratch.opcode = EEOP_WINDOW_FUNC;
                scratch.d.window_func.wfstate = wfstate;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ArrayRef:
            {
                ArrayRef   *aref = (ArrayRef *) node;

                ExecInitArrayRef(&scratch, aref, parent, state, resv, resnull);
                break;
            }

        case T_FuncExpr:
            {
                FuncExpr   *func = (FuncExpr *) node;

                ExecInitFunc(&scratch, node,
                             func->args, func->funcid, func->inputcollid,
                             parent, state);
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_OpExpr:
            {
                OpExpr       *op = (OpExpr *) node;

                ExecInitFunc(&scratch, node,
                             op->args, op->opfuncid, op->inputcollid,
                             parent, state);
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_DistinctExpr:
            {
                DistinctExpr *op = (DistinctExpr *) node;

                ExecInitFunc(&scratch, node,
                             op->args, op->opfuncid, op->inputcollid,
                             parent, state);

                /*
                 * Change opcode of call instruction to EEOP_DISTINCT.
                 *
                 * XXX: historically we've not called the function usage
                 * pgstat infrastructure - that seems inconsistent given that
                 * we do so for normal function *and* operator evaluation.  If
                 * we decided to do that here, we'd probably want separate
                 * opcodes for FUSAGE or not.
                 */
                scratch.opcode = EEOP_DISTINCT;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_NullIfExpr:
            {
                NullIfExpr *op = (NullIfExpr *) node;

                ExecInitFunc(&scratch, node,
                             op->args, op->opfuncid, op->inputcollid,
                             parent, state);

                /*
                 * Change opcode of call instruction to EEOP_NULLIF.
                 *
                 * XXX: historically we've not called the function usage
                 * pgstat infrastructure - that seems inconsistent given that
                 * we do so for normal function *and* operator evaluation.  If
                 * we decided to do that here, we'd probably want separate
                 * opcodes for FUSAGE or not.
                 */
                scratch.opcode = EEOP_NULLIF;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ScalarArrayOpExpr:
            {
                ScalarArrayOpExpr *opexpr = (ScalarArrayOpExpr *) node;
                Expr       *scalararg;
                Expr       *arrayarg;
                FmgrInfo   *finfo;
                FunctionCallInfo fcinfo;
                AclResult    aclresult;

                Assert(list_length(opexpr->args) == 2);
                scalararg = (Expr *) linitial(opexpr->args);
                arrayarg = (Expr *) lsecond(opexpr->args);

                /* Check permission to call function */
                aclresult = pg_proc_aclcheck(opexpr->opfuncid,
                                             GetUserId(),
                                             ACL_EXECUTE);
                if (aclresult != ACLCHECK_OK)
                    aclcheck_error(aclresult, ACL_KIND_PROC,
                                   get_func_name(opexpr->opfuncid));
                InvokeFunctionExecuteHook(opexpr->opfuncid);

                /* Set up the primary fmgr lookup information */
                finfo = palloc0(sizeof(FmgrInfo));
                fcinfo = palloc0(sizeof(FunctionCallInfoData));
                fmgr_info(opexpr->opfuncid, finfo);
                fmgr_info_set_expr((Node *) node, finfo);
                InitFunctionCallInfoData(*fcinfo, finfo, 2,
                                         opexpr->inputcollid, NULL, NULL);

                /* Evaluate scalar directly into left function argument */
                ExecInitExprRec(scalararg, parent, state,
                                &fcinfo->arg[0], &fcinfo->argnull[0]);

                /*
                 * Evaluate array argument into our return value.  There's no
                 * danger in that, because the return value is guaranteed to
                 * be overwritten by EEOP_SCALARARRAYOP, and will not be
                 * passed to any other expression.
                 */
                ExecInitExprRec(arrayarg, parent, state, resv, resnull);

                /* And perform the operation */
                scratch.opcode = EEOP_SCALARARRAYOP;
                scratch.d.scalararrayop.element_type = InvalidOid;
                scratch.d.scalararrayop.useOr = opexpr->useOr;
                scratch.d.scalararrayop.finfo = finfo;
                scratch.d.scalararrayop.fcinfo_data = fcinfo;
                scratch.d.scalararrayop.fn_addr = finfo->fn_addr;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_BoolExpr:
            {
                BoolExpr   *boolexpr = (BoolExpr *) node;
                int            nargs = list_length(boolexpr->args);
                List       *adjust_jumps = NIL;
                int            off;
                ListCell   *lc;

                /* allocate scratch memory used by all steps of AND/OR */
                if (boolexpr->boolop != NOT_EXPR)
                    scratch.d.boolexpr.anynull = (bool *) palloc(sizeof(bool));

                /*
                 * For each argument evaluate the argument itself, then
                 * perform the bool operation's appropriate handling.
                 *
                 * We can evaluate each argument into our result area, since
                 * the short-circuiting logic means we only need to remember
                 * previous NULL values.
                 *
                 * AND/OR is split into separate STEP_FIRST (one) / STEP (zero
                 * or more) / STEP_LAST (one) steps, as each of those has to
                 * perform different work.  The FIRST/LAST split is valid
                 * because AND/OR have at least two arguments.
                 */
                off = 0;
                foreach(lc, boolexpr->args)
                {
                    Expr       *arg = (Expr *) lfirst(lc);

                    /* Evaluate argument into our output variable */
                    ExecInitExprRec(arg, parent, state, resv, resnull);

                    /* Perform the appropriate step type */
                    switch (boolexpr->boolop)
                    {
                        case AND_EXPR:
                            Assert(nargs >= 2);

                            if (off == 0)
                                scratch.opcode = EEOP_BOOL_AND_STEP_FIRST;
                            else if (off + 1 == nargs)
                                scratch.opcode = EEOP_BOOL_AND_STEP_LAST;
                            else
                                scratch.opcode = EEOP_BOOL_AND_STEP;
                            break;
                        case OR_EXPR:
                            Assert(nargs >= 2);

                            if (off == 0)
                                scratch.opcode = EEOP_BOOL_OR_STEP_FIRST;
                            else if (off + 1 == nargs)
                                scratch.opcode = EEOP_BOOL_OR_STEP_LAST;
                            else
                                scratch.opcode = EEOP_BOOL_OR_STEP;
                            break;
                        case NOT_EXPR:
                            Assert(nargs == 1);

                            scratch.opcode = EEOP_BOOL_NOT_STEP;
                            break;
                        default:
                            elog(ERROR, "unrecognized boolop: %d",
                                 (int) boolexpr->boolop);
                            break;
                    }

                    scratch.d.boolexpr.jumpdone = -1;
                    ExprEvalPushStep(state, &scratch);
                    adjust_jumps = lappend_int(adjust_jumps,
                                               state->steps_len - 1);
                    off++;
                }

                /* adjust jump targets */
                foreach(lc, adjust_jumps)
                {
                    ExprEvalStep *as = &state->steps[lfirst_int(lc)];

                    Assert(as->d.boolexpr.jumpdone == -1);
                    as->d.boolexpr.jumpdone = state->steps_len;
                }

                break;
            }

        case T_SubPlan:
            {
                SubPlan    *subplan = (SubPlan *) node;
                SubPlanState *sstate;

                if (!parent)
                    elog(ERROR, "SubPlan found with no parent plan");

                sstate = ExecInitSubPlan(subplan, parent);

                /* add SubPlanState nodes to parent->subPlan */
                parent->subPlan = lappend(parent->subPlan, sstate);

                scratch.opcode = EEOP_SUBPLAN;
                scratch.d.subplan.sstate = sstate;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_AlternativeSubPlan:
            {
                AlternativeSubPlan *asplan = (AlternativeSubPlan *) node;
                AlternativeSubPlanState *asstate;

                if (!parent)
                    elog(ERROR, "AlternativeSubPlan found with no parent plan");

                asstate = ExecInitAlternativeSubPlan(asplan, parent);

                scratch.opcode = EEOP_ALTERNATIVE_SUBPLAN;
                scratch.d.alternative_subplan.asstate = asstate;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_FieldSelect:
            {
                FieldSelect *fselect = (FieldSelect *) node;

                /* evaluate row/record argument into result area */
                ExecInitExprRec(fselect->arg, parent, state, resv, resnull);

                /* and extract field */
                scratch.opcode = EEOP_FIELDSELECT;
                scratch.d.fieldselect.fieldnum = fselect->fieldnum;
                scratch.d.fieldselect.resulttype = fselect->resulttype;
                scratch.d.fieldselect.argdesc = NULL;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_FieldStore:
            {
                FieldStore *fstore = (FieldStore *) node;
                TupleDesc    tupDesc;
                TupleDesc  *descp;
                Datum       *values;
                bool       *nulls;
                int            ncolumns;
                ListCell   *l1,
                           *l2;

                /* find out the number of columns in the composite type */
                tupDesc = lookup_rowtype_tupdesc(fstore->resulttype, -1);
                ncolumns = tupDesc->natts;
                DecrTupleDescRefCount(tupDesc);

                /* create workspace for column values */
                values = (Datum *) palloc(sizeof(Datum) * ncolumns);
                nulls = (bool *) palloc(sizeof(bool) * ncolumns);

                /* create workspace for runtime tupdesc cache */
                descp = (TupleDesc *) palloc(sizeof(TupleDesc));
                *descp = NULL;

                /* emit code to evaluate the composite input value */
                ExecInitExprRec(fstore->arg, parent, state, resv, resnull);

                /* next, deform the input tuple into our workspace */
                scratch.opcode = EEOP_FIELDSTORE_DEFORM;
                scratch.d.fieldstore.fstore = fstore;
                scratch.d.fieldstore.argdesc = descp;
                scratch.d.fieldstore.values = values;
                scratch.d.fieldstore.nulls = nulls;
                scratch.d.fieldstore.ncolumns = ncolumns;
                ExprEvalPushStep(state, &scratch);

                /* evaluate new field values, store in workspace columns */
                forboth(l1, fstore->newvals, l2, fstore->fieldnums)
                {
                    Expr       *e = (Expr *) lfirst(l1);
                    AttrNumber    fieldnum = lfirst_int(l2);
                    Datum       *save_innermost_caseval;
                    bool       *save_innermost_casenull;

                    if (fieldnum <= 0 || fieldnum > ncolumns)
                        elog(ERROR, "field number %d is out of range in FieldStore",
                             fieldnum);

                    /*
                     * Use the CaseTestExpr mechanism to pass down the old
                     * value of the field being replaced; this is needed in
                     * case the newval is itself a FieldStore or ArrayRef that
                     * has to obtain and modify the old value.  It's safe to
                     * reuse the CASE mechanism because there cannot be a CASE
                     * between here and where the value would be needed, and a
                     * field assignment can't be within a CASE either.  (So
                     * saving and restoring innermost_caseval is just
                     * paranoia, but let's do it anyway.)
                     *
                     * Another non-obvious point is that it's safe to use the
                     * field's values[]/nulls[] entries as both the caseval
                     * source and the result address for this subexpression.
                     * That's okay only because (1) both FieldStore and
                     * ArrayRef evaluate their arg or refexpr inputs first,
                     * and (2) any such CaseTestExpr is directly the arg or
                     * refexpr input.  So any read of the caseval will occur
                     * before there's a chance to overwrite it.  Also, if
                     * multiple entries in the newvals/fieldnums lists target
                     * the same field, they'll effectively be applied
                     * left-to-right which is what we want.
                     */
                    save_innermost_caseval = state->innermost_caseval;
                    save_innermost_casenull = state->innermost_casenull;
                    state->innermost_caseval = &values[fieldnum - 1];
                    state->innermost_casenull = &nulls[fieldnum - 1];

                    ExecInitExprRec(e, parent, state,
                                    &values[fieldnum - 1],
                                    &nulls[fieldnum - 1]);

                    state->innermost_caseval = save_innermost_caseval;
                    state->innermost_casenull = save_innermost_casenull;
                }

                /* finally, form result tuple */
                scratch.opcode = EEOP_FIELDSTORE_FORM;
                scratch.d.fieldstore.fstore = fstore;
                scratch.d.fieldstore.argdesc = descp;
                scratch.d.fieldstore.values = values;
                scratch.d.fieldstore.nulls = nulls;
                scratch.d.fieldstore.ncolumns = ncolumns;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_RelabelType:
            {
                /* relabel doesn't need to do anything at runtime */
                RelabelType *relabel = (RelabelType *) node;

                ExecInitExprRec(relabel->arg, parent, state, resv, resnull);
                break;
            }

        case T_CoerceViaIO:
            {
                CoerceViaIO *iocoerce = (CoerceViaIO *) node;
                Oid            iofunc;
                bool        typisvarlena;
                Oid            typioparam;
                FunctionCallInfo fcinfo_in;

                /* evaluate argument into step's result area */
                ExecInitExprRec(iocoerce->arg, parent, state, resv, resnull);

                /*
                 * Prepare both output and input function calls, to be
                 * evaluated inside a single evaluation step for speed - this
                 * can be a very common operation.
                 *
                 * We don't check permissions here as a type's input/output
                 * function are assumed to be executable by everyone.
                 */
                scratch.opcode = EEOP_IOCOERCE;

                /* lookup the source type's output function */
                scratch.d.iocoerce.finfo_out = palloc0(sizeof(FmgrInfo));
                scratch.d.iocoerce.fcinfo_data_out = palloc0(sizeof(FunctionCallInfoData));

                getTypeOutputInfo(exprType((Node *) iocoerce->arg),
                                  &iofunc, &typisvarlena);
                fmgr_info(iofunc, scratch.d.iocoerce.finfo_out);
                fmgr_info_set_expr((Node *) node, scratch.d.iocoerce.finfo_out);
                InitFunctionCallInfoData(*scratch.d.iocoerce.fcinfo_data_out,
                                         scratch.d.iocoerce.finfo_out,
                                         1, InvalidOid, NULL, NULL);

                /* lookup the result type's input function */
                scratch.d.iocoerce.finfo_in = palloc0(sizeof(FmgrInfo));
                scratch.d.iocoerce.fcinfo_data_in = palloc0(sizeof(FunctionCallInfoData));

                getTypeInputInfo(iocoerce->resulttype,
                                 &iofunc, &typioparam);
                fmgr_info(iofunc, scratch.d.iocoerce.finfo_in);
                fmgr_info_set_expr((Node *) node, scratch.d.iocoerce.finfo_in);
                InitFunctionCallInfoData(*scratch.d.iocoerce.fcinfo_data_in,
                                         scratch.d.iocoerce.finfo_in,
                                         3, InvalidOid, NULL, NULL);

                /*
                 * We can preload the second and third arguments for the input
                 * function, since they're constants.
                 */
                fcinfo_in = scratch.d.iocoerce.fcinfo_data_in;
                fcinfo_in->arg[1] = ObjectIdGetDatum(typioparam);
                fcinfo_in->argnull[1] = false;
                fcinfo_in->arg[2] = Int32GetDatum(-1);
                fcinfo_in->argnull[2] = false;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ArrayCoerceExpr:
            {
                ArrayCoerceExpr *acoerce = (ArrayCoerceExpr *) node;
                Oid            resultelemtype;

                /* evaluate argument into step's result area */
                ExecInitExprRec(acoerce->arg, parent, state, resv, resnull);

                resultelemtype = get_element_type(acoerce->resulttype);
                if (!OidIsValid(resultelemtype))
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("target type is not an array")));
                /* Arrays over domains aren't supported yet */
                Assert(getBaseType(resultelemtype) == resultelemtype);

                scratch.opcode = EEOP_ARRAYCOERCE;
                scratch.d.arraycoerce.coerceexpr = acoerce;
                scratch.d.arraycoerce.resultelemtype = resultelemtype;

                if (OidIsValid(acoerce->elemfuncid))
                {
                    AclResult    aclresult;

                    /* Check permission to call function */
                    aclresult = pg_proc_aclcheck(acoerce->elemfuncid,
                                                 GetUserId(),
                                                 ACL_EXECUTE);
                    if (aclresult != ACLCHECK_OK)
                        aclcheck_error(aclresult, ACL_KIND_PROC,
                                       get_func_name(acoerce->elemfuncid));
                    InvokeFunctionExecuteHook(acoerce->elemfuncid);

                    /* Set up the primary fmgr lookup information */
                    scratch.d.arraycoerce.elemfunc =
                        (FmgrInfo *) palloc0(sizeof(FmgrInfo));
                    fmgr_info(acoerce->elemfuncid,
                              scratch.d.arraycoerce.elemfunc);
                    fmgr_info_set_expr((Node *) acoerce,
                                       scratch.d.arraycoerce.elemfunc);

                    /* Set up workspace for array_map */
                    scratch.d.arraycoerce.amstate =
                        (ArrayMapState *) palloc0(sizeof(ArrayMapState));
                }
                else
                {
                    /* Don't need workspace if there's no conversion func */
                    scratch.d.arraycoerce.elemfunc = NULL;
                    scratch.d.arraycoerce.amstate = NULL;
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ConvertRowtypeExpr:
            {
                ConvertRowtypeExpr *convert = (ConvertRowtypeExpr *) node;

                /* evaluate argument into step's result area */
                ExecInitExprRec(convert->arg, parent, state, resv, resnull);

                /* and push conversion step */
                scratch.opcode = EEOP_CONVERT_ROWTYPE;
                scratch.d.convert_rowtype.convert = convert;
                scratch.d.convert_rowtype.indesc = NULL;
                scratch.d.convert_rowtype.outdesc = NULL;
                scratch.d.convert_rowtype.map = NULL;
                scratch.d.convert_rowtype.initialized = false;

                ExprEvalPushStep(state, &scratch);
                break;
            }

            /* note that CaseWhen expressions are handled within this block */
        case T_CaseExpr:
            {
                CaseExpr   *caseExpr = (CaseExpr *) node;
                List       *adjust_jumps = NIL;
                Datum       *caseval = NULL;
                bool       *casenull = NULL;
                ListCell   *lc;

                /*
                 * If there's a test expression, we have to evaluate it and
                 * save the value where the CaseTestExpr placeholders can find
                 * it.
                 */
                if (caseExpr->arg != NULL)
                {
                    /* Evaluate testexpr into caseval/casenull workspace */
                    caseval = palloc(sizeof(Datum));
                    casenull = palloc(sizeof(bool));

                    ExecInitExprRec(caseExpr->arg, parent, state,
                                    caseval, casenull);

                    /*
                     * Since value might be read multiple times, force to R/O
                     * - but only if it could be an expanded datum.
                     */
                    if (get_typlen(exprType((Node *) caseExpr->arg)) == -1)
                    {
                        /* change caseval in-place */
                        scratch.opcode = EEOP_MAKE_READONLY;
                        scratch.resvalue = caseval;
                        scratch.resnull = casenull;
                        scratch.d.make_readonly.value = caseval;
                        scratch.d.make_readonly.isnull = casenull;
                        ExprEvalPushStep(state, &scratch);
                        /* restore normal settings of scratch fields */
                        scratch.resvalue = resv;
                        scratch.resnull = resnull;
                    }
                }

                /*
                 * Prepare to evaluate each of the WHEN clauses in turn; as
                 * soon as one is true we return the value of the
                 * corresponding THEN clause.  If none are true then we return
                 * the value of the ELSE clause, or NULL if there is none.
                 */
                foreach(lc, caseExpr->args)
                {
                    CaseWhen   *when = (CaseWhen *) lfirst(lc);
                    Datum       *save_innermost_caseval;
                    bool       *save_innermost_casenull;
                    int            whenstep;

                    /*
                     * Make testexpr result available to CaseTestExpr nodes
                     * within the condition.  We must save and restore prior
                     * setting of innermost_caseval fields, in case this node
                     * is itself within a larger CASE.
                     *
                     * If there's no test expression, we don't actually need
                     * to save and restore these fields; but it's less code to
                     * just do so unconditionally.
                     */
                    save_innermost_caseval = state->innermost_caseval;
                    save_innermost_casenull = state->innermost_casenull;
                    state->innermost_caseval = caseval;
                    state->innermost_casenull = casenull;

                    /* evaluate condition into CASE's result variables */
                    ExecInitExprRec(when->expr, parent, state, resv, resnull);

                    state->innermost_caseval = save_innermost_caseval;
                    state->innermost_casenull = save_innermost_casenull;

                    /* If WHEN result isn't true, jump to next CASE arm */
                    scratch.opcode = EEOP_JUMP_IF_NOT_TRUE;
                    scratch.d.jump.jumpdone = -1;    /* computed later */
                    ExprEvalPushStep(state, &scratch);
                    whenstep = state->steps_len - 1;

                    /*
                     * If WHEN result is true, evaluate THEN result, storing
                     * it into the CASE's result variables.
                     */
                    ExecInitExprRec(when->result, parent, state, resv, resnull);

                    /* Emit JUMP step to jump to end of CASE's code */
                    scratch.opcode = EEOP_JUMP;
                    scratch.d.jump.jumpdone = -1;    /* computed later */
                    ExprEvalPushStep(state, &scratch);

                    /*
                     * Don't know address for that jump yet, compute once the
                     * whole CASE expression is built.
                     */
                    adjust_jumps = lappend_int(adjust_jumps,
                                               state->steps_len - 1);

                    /*
                     * But we can set WHEN test's jump target now, to make it
                     * jump to the next WHEN subexpression or the ELSE.
                     */
                    state->steps[whenstep].d.jump.jumpdone = state->steps_len;
                }

                /* transformCaseExpr always adds a default */
                Assert(caseExpr->defresult);

                /* evaluate ELSE expr into CASE's result variables */
                ExecInitExprRec(caseExpr->defresult, parent, state,
                                resv, resnull);

                /* adjust jump targets */
                foreach(lc, adjust_jumps)
                {
                    ExprEvalStep *as = &state->steps[lfirst_int(lc)];

                    Assert(as->opcode == EEOP_JUMP);
                    Assert(as->d.jump.jumpdone == -1);
                    as->d.jump.jumpdone = state->steps_len;
                }

                break;
            }

        case T_CaseTestExpr:
            {
                /*
                 * Read from location identified by innermost_caseval.  Note
                 * that innermost_caseval could be NULL, if this node isn't
                 * actually within a CASE structure; some parts of the system
                 * abuse CaseTestExpr to cause a read of a value externally
                 * supplied in econtext->caseValue_datum.  We'll take care of
                 * that scenario at runtime.
                 */
                scratch.opcode = EEOP_CASE_TESTVAL;
                scratch.d.casetest.value = state->innermost_caseval;
                scratch.d.casetest.isnull = state->innermost_casenull;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_ArrayExpr:
            {
                ArrayExpr  *arrayexpr = (ArrayExpr *) node;
                int            nelems = list_length(arrayexpr->elements);
                ListCell   *lc;
                int            elemoff;

                /*
                 * Evaluate by computing each element, and then forming the
                 * array.  Elements are computed into scratch arrays
                 * associated with the ARRAYEXPR step.
                 */
                scratch.opcode = EEOP_ARRAYEXPR;
                scratch.d.arrayexpr.elemvalues =
                    (Datum *) palloc(sizeof(Datum) * nelems);
                scratch.d.arrayexpr.elemnulls =
                    (bool *) palloc(sizeof(bool) * nelems);
                scratch.d.arrayexpr.nelems = nelems;

                /* fill remaining fields of step */
                scratch.d.arrayexpr.multidims = arrayexpr->multidims;
                scratch.d.arrayexpr.elemtype = arrayexpr->element_typeid;

                /* do one-time catalog lookup for type info */
                get_typlenbyvalalign(arrayexpr->element_typeid,
                                     &scratch.d.arrayexpr.elemlength,
                                     &scratch.d.arrayexpr.elembyval,
                                     &scratch.d.arrayexpr.elemalign);

                /* prepare to evaluate all arguments */
                elemoff = 0;
                foreach(lc, arrayexpr->elements)
                {
                    Expr       *e = (Expr *) lfirst(lc);

                    ExecInitExprRec(e, parent, state,
                                    &scratch.d.arrayexpr.elemvalues[elemoff],
                                    &scratch.d.arrayexpr.elemnulls[elemoff]);
                    elemoff++;
                }

                /* and then collect all into an array */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_RowExpr:
            {
                RowExpr    *rowexpr = (RowExpr *) node;
                int            nelems = list_length(rowexpr->args);
                TupleDesc    tupdesc;
                Form_pg_attribute *attrs;
                int            i;
                ListCell   *l;

                /* Build tupdesc to describe result tuples */
                if (rowexpr->row_typeid == RECORDOID)
                {
                    /* generic record, use types of given expressions */
                    tupdesc = ExecTypeFromExprList(rowexpr->args);
                }
                else
                {
                    /* it's been cast to a named type, use that */
                    tupdesc = lookup_rowtype_tupdesc_copy(rowexpr->row_typeid, -1);
                }
                /* In either case, adopt RowExpr's column aliases */
                ExecTypeSetColNames(tupdesc, rowexpr->colnames);
                /* Bless the tupdesc in case it's now of type RECORD */
                BlessTupleDesc(tupdesc);

                /*
                 * In the named-type case, the tupdesc could have more columns
                 * than are in the args list, since the type might have had
                 * columns added since the ROW() was parsed.  We want those
                 * extra columns to go to nulls, so we make sure that the
                 * workspace arrays are large enough and then initialize any
                 * extra columns to read as NULLs.
                 */
                Assert(nelems <= tupdesc->natts);
                nelems = Max(nelems, tupdesc->natts);

                /*
                 * Evaluate by first building datums for each field, and then
                 * a final step forming the composite datum.
                 */
                scratch.opcode = EEOP_ROW;
                scratch.d.row.tupdesc = tupdesc;

                /* space for the individual field datums */
                scratch.d.row.elemvalues =
                    (Datum *) palloc(sizeof(Datum) * nelems);
                scratch.d.row.elemnulls =
                    (bool *) palloc(sizeof(bool) * nelems);
                /* as explained above, make sure any extra columns are null */
                memset(scratch.d.row.elemnulls, true, sizeof(bool) * nelems);

                /* Set up evaluation, skipping any deleted columns */
                attrs = tupdesc->attrs;
                i = 0;
                foreach(l, rowexpr->args)
                {
                    Expr       *e = (Expr *) lfirst(l);

                    if (!attrs[i]->attisdropped)
                    {
                        /*
                         * Guard against ALTER COLUMN TYPE on rowtype since
                         * the RowExpr was created.  XXX should we check
                         * typmod too?    Not sure we can be sure it'll be the
                         * same.
                         */
                        if (exprType((Node *) e) != attrs[i]->atttypid)
                            ereport(ERROR,
                                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                                     errmsg("ROW() column has type %s instead of type %s",
                                            format_type_be(exprType((Node *) e)),
                                            format_type_be(attrs[i]->atttypid))));
                    }
                    else
                    {
                        /*
                         * Ignore original expression and insert a NULL. We
                         * don't really care what type of NULL it is, so
                         * always make an int4 NULL.
                         */
                        e = (Expr *) makeNullConst(INT4OID, -1, InvalidOid);
                    }

                    /* Evaluate column expr into appropriate workspace slot */
                    ExecInitExprRec(e, parent, state,
                                    &scratch.d.row.elemvalues[i],
                                    &scratch.d.row.elemnulls[i]);
                    i++;
                }

                /* And finally build the row value */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_RowCompareExpr:
            {
                RowCompareExpr *rcexpr = (RowCompareExpr *) node;
                int            nopers = list_length(rcexpr->opnos);
                List       *adjust_jumps = NIL;
                ListCell   *l_left_expr,
                           *l_right_expr,
                           *l_opno,
                           *l_opfamily,
                           *l_inputcollid;
                ListCell   *lc;
                int            off;

                /*
                 * Iterate over each field, prepare comparisons.  To handle
                 * NULL results, prepare jumps to after the expression.  If a
                 * comparison yields a != 0 result, jump to the final step.
                 */
                Assert(list_length(rcexpr->largs) == nopers);
                Assert(list_length(rcexpr->rargs) == nopers);
                Assert(list_length(rcexpr->opfamilies) == nopers);
                Assert(list_length(rcexpr->inputcollids) == nopers);

                off = 0;
                for (off = 0,
                     l_left_expr = list_head(rcexpr->largs),
                     l_right_expr = list_head(rcexpr->rargs),
                     l_opno = list_head(rcexpr->opnos),
                     l_opfamily = list_head(rcexpr->opfamilies),
                     l_inputcollid = list_head(rcexpr->inputcollids);
                     off < nopers;
                     off++,
                     l_left_expr = lnext(l_left_expr),
                     l_right_expr = lnext(l_right_expr),
                     l_opno = lnext(l_opno),
                     l_opfamily = lnext(l_opfamily),
                     l_inputcollid = lnext(l_inputcollid))
                {
                    Expr       *left_expr = (Expr *) lfirst(l_left_expr);
                    Expr       *right_expr = (Expr *) lfirst(l_right_expr);
                    Oid            opno = lfirst_oid(l_opno);
                    Oid            opfamily = lfirst_oid(l_opfamily);
                    Oid            inputcollid = lfirst_oid(l_inputcollid);
                    int            strategy;
                    Oid            lefttype;
                    Oid            righttype;
                    Oid            proc;
                    FmgrInfo   *finfo;
                    FunctionCallInfo fcinfo;

                    get_op_opfamily_properties(opno, opfamily, false,
                                               &strategy,
                                               &lefttype,
                                               &righttype);
                    proc = get_opfamily_proc(opfamily,
                                             lefttype,
                                             righttype,
                                             BTORDER_PROC);
                    if (!OidIsValid(proc))
                        elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
                             BTORDER_PROC, lefttype, righttype, opfamily);

                    /* Set up the primary fmgr lookup information */
                    finfo = palloc0(sizeof(FmgrInfo));
                    fcinfo = palloc0(sizeof(FunctionCallInfoData));
                    fmgr_info(proc, finfo);
                    fmgr_info_set_expr((Node *) node, finfo);
                    InitFunctionCallInfoData(*fcinfo, finfo, 2,
                                             inputcollid, NULL, NULL);

                    /*
                     * If we enforced permissions checks on index support
                     * functions, we'd need to make a check here.  But the
                     * index support machinery doesn't do that, and thus
                     * neither does this code.
                     */

                    /* evaluate left and right args directly into fcinfo */
                    ExecInitExprRec(left_expr, parent, state,
                                    &fcinfo->arg[0], &fcinfo->argnull[0]);
                    ExecInitExprRec(right_expr, parent, state,
                                    &fcinfo->arg[1], &fcinfo->argnull[1]);

                    scratch.opcode = EEOP_ROWCOMPARE_STEP;
                    scratch.d.rowcompare_step.finfo = finfo;
                    scratch.d.rowcompare_step.fcinfo_data = fcinfo;
                    scratch.d.rowcompare_step.fn_addr = finfo->fn_addr;
                    /* jump targets filled below */
                    scratch.d.rowcompare_step.jumpnull = -1;
                    scratch.d.rowcompare_step.jumpdone = -1;

                    ExprEvalPushStep(state, &scratch);
                    adjust_jumps = lappend_int(adjust_jumps,
                                               state->steps_len - 1);
                }

                /*
                 * We could have a zero-column rowtype, in which case the rows
                 * necessarily compare equal.
                 */
                if (nopers == 0)
                {
                    scratch.opcode = EEOP_CONST;
                    scratch.d.constval.value = Int32GetDatum(0);
                    scratch.d.constval.isnull = false;
                    ExprEvalPushStep(state, &scratch);
                }

                /* Finally, examine the last comparison result */
                scratch.opcode = EEOP_ROWCOMPARE_FINAL;
                scratch.d.rowcompare_final.rctype = rcexpr->rctype;
                ExprEvalPushStep(state, &scratch);

                /* adjust jump targetss */
                foreach(lc, adjust_jumps)
                {
                    ExprEvalStep *as = &state->steps[lfirst_int(lc)];

                    Assert(as->opcode == EEOP_ROWCOMPARE_STEP);
                    Assert(as->d.rowcompare_step.jumpdone == -1);
                    Assert(as->d.rowcompare_step.jumpnull == -1);

                    /* jump to comparison evaluation */
                    as->d.rowcompare_step.jumpdone = state->steps_len - 1;
                    /* jump to the following expression */
                    as->d.rowcompare_step.jumpnull = state->steps_len;
                }

                break;
            }

        case T_CoalesceExpr:
            {
                CoalesceExpr *coalesce = (CoalesceExpr *) node;
                List       *adjust_jumps = NIL;
                ListCell   *lc;

                /* We assume there's at least one arg */
                Assert(coalesce->args != NIL);

                /*
                 * Prepare evaluation of all coalesced arguments, after each
                 * one push a step that short-circuits if not null.
                 */
                foreach(lc, coalesce->args)
                {
                    Expr       *e = (Expr *) lfirst(lc);

                    /* evaluate argument, directly into result datum */
                    ExecInitExprRec(e, parent, state, resv, resnull);

                    /* if it's not null, skip to end of COALESCE expr */
                    scratch.opcode = EEOP_JUMP_IF_NOT_NULL;
                    scratch.d.jump.jumpdone = -1;    /* adjust later */
                    ExprEvalPushStep(state, &scratch);

                    adjust_jumps = lappend_int(adjust_jumps,
                                               state->steps_len - 1);
                }

                /*
                 * No need to add a constant NULL return - we only can get to
                 * the end of the expression if a NULL already is being
                 * returned.
                 */

                /* adjust jump targets */
                foreach(lc, adjust_jumps)
                {
                    ExprEvalStep *as = &state->steps[lfirst_int(lc)];

                    Assert(as->opcode == EEOP_JUMP_IF_NOT_NULL);
                    Assert(as->d.jump.jumpdone == -1);
                    as->d.jump.jumpdone = state->steps_len;
                }

                break;
            }

        case T_MinMaxExpr:
            {
                MinMaxExpr *minmaxexpr = (MinMaxExpr *) node;
                int            nelems = list_length(minmaxexpr->args);
                TypeCacheEntry *typentry;
                FmgrInfo   *finfo;
                FunctionCallInfo fcinfo;
                ListCell   *lc;
                int            off;

                /* Look up the btree comparison function for the datatype */
                typentry = lookup_type_cache(minmaxexpr->minmaxtype,
                                             TYPECACHE_CMP_PROC);
                if (!OidIsValid(typentry->cmp_proc))
                    ereport(ERROR,
                            (errcode(ERRCODE_UNDEFINED_FUNCTION),
                             errmsg("could not identify a comparison function for type %s",
                                    format_type_be(minmaxexpr->minmaxtype))));

                /*
                 * If we enforced permissions checks on index support
                 * functions, we'd need to make a check here.  But the index
                 * support machinery doesn't do that, and thus neither does
                 * this code.
                 */

                /* Perform function lookup */
                finfo = palloc0(sizeof(FmgrInfo));
                fcinfo = palloc0(sizeof(FunctionCallInfoData));
                fmgr_info(typentry->cmp_proc, finfo);
                fmgr_info_set_expr((Node *) node, finfo);
                InitFunctionCallInfoData(*fcinfo, finfo, 2,
                                         minmaxexpr->inputcollid, NULL, NULL);

                scratch.opcode = EEOP_MINMAX;
                /* allocate space to store arguments */
                scratch.d.minmax.values =
                    (Datum *) palloc(sizeof(Datum) * nelems);
                scratch.d.minmax.nulls =
                    (bool *) palloc(sizeof(bool) * nelems);
                scratch.d.minmax.nelems = nelems;

                scratch.d.minmax.op = minmaxexpr->op;
                scratch.d.minmax.finfo = finfo;
                scratch.d.minmax.fcinfo_data = fcinfo;

                /* evaluate expressions into minmax->values/nulls */
                off = 0;
                foreach(lc, minmaxexpr->args)
                {
                    Expr       *e = (Expr *) lfirst(lc);

                    ExecInitExprRec(e, parent, state,
                                    &scratch.d.minmax.values[off],
                                    &scratch.d.minmax.nulls[off]);
                    off++;
                }

                /* and push the final comparison */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_SQLValueFunction:
            {
                SQLValueFunction *svf = (SQLValueFunction *) node;

                scratch.opcode = EEOP_SQLVALUEFUNCTION;
                scratch.d.sqlvaluefunction.svf = svf;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_XmlExpr:
            {
                XmlExpr    *xexpr = (XmlExpr *) node;
                int            nnamed = list_length(xexpr->named_args);
                int            nargs = list_length(xexpr->args);
                int            off;
                ListCell   *arg;

                scratch.opcode = EEOP_XMLEXPR;
                scratch.d.xmlexpr.xexpr = xexpr;

                /* allocate space for storing all the arguments */
                if (nnamed)
                {
                    scratch.d.xmlexpr.named_argvalue =
                        (Datum *) palloc(sizeof(Datum) * nnamed);
                    scratch.d.xmlexpr.named_argnull =
                        (bool *) palloc(sizeof(bool) * nnamed);
                }
                else
                {
                    scratch.d.xmlexpr.named_argvalue = NULL;
                    scratch.d.xmlexpr.named_argnull = NULL;
                }

                if (nargs)
                {
                    scratch.d.xmlexpr.argvalue =
                        (Datum *) palloc(sizeof(Datum) * nargs);
                    scratch.d.xmlexpr.argnull =
                        (bool *) palloc(sizeof(bool) * nargs);
                }
                else
                {
                    scratch.d.xmlexpr.argvalue = NULL;
                    scratch.d.xmlexpr.argnull = NULL;
                }

                /* prepare argument execution */
                off = 0;
                foreach(arg, xexpr->named_args)
                {
                    Expr       *e = (Expr *) lfirst(arg);

                    ExecInitExprRec(e, parent, state,
                                    &scratch.d.xmlexpr.named_argvalue[off],
                                    &scratch.d.xmlexpr.named_argnull[off]);
                    off++;
                }

                off = 0;
                foreach(arg, xexpr->args)
                {
                    Expr       *e = (Expr *) lfirst(arg);

                    ExecInitExprRec(e, parent, state,
                                    &scratch.d.xmlexpr.argvalue[off],
                                    &scratch.d.xmlexpr.argnull[off]);
                    off++;
                }

                /* and evaluate the actual XML expression */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_NullTest:
            {
                NullTest   *ntest = (NullTest *) node;

                if (ntest->nulltesttype == IS_NULL)
                {
                    if (ntest->argisrow)
                        scratch.opcode = EEOP_NULLTEST_ROWISNULL;
                    else
                        scratch.opcode = EEOP_NULLTEST_ISNULL;
                }
                else if (ntest->nulltesttype == IS_NOT_NULL)
                {
                    if (ntest->argisrow)
                        scratch.opcode = EEOP_NULLTEST_ROWISNOTNULL;
                    else
                        scratch.opcode = EEOP_NULLTEST_ISNOTNULL;
                }
                else
                {
                    elog(ERROR, "unrecognized nulltesttype: %d",
                         (int) ntest->nulltesttype);
                }
                /* initialize cache in case it's a row test */
                scratch.d.nulltest_row.argdesc = NULL;

                /* first evaluate argument into result variable */
                ExecInitExprRec(ntest->arg, parent, state,
                                resv, resnull);

                /* then push the test of that argument */
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_BooleanTest:
            {
                BooleanTest *btest = (BooleanTest *) node;

                /*
                 * Evaluate argument, directly into result datum.  That's ok,
                 * because resv/resnull is definitely not used anywhere else,
                 * and will get overwritten by the below EEOP_BOOLTEST_IS_*
                 * step.
                 */
                ExecInitExprRec(btest->arg, parent, state, resv, resnull);

                switch (btest->booltesttype)
                {
                    case IS_TRUE:
                        scratch.opcode = EEOP_BOOLTEST_IS_TRUE;
                        break;
                    case IS_NOT_TRUE:
                        scratch.opcode = EEOP_BOOLTEST_IS_NOT_TRUE;
                        break;
                    case IS_FALSE:
                        scratch.opcode = EEOP_BOOLTEST_IS_FALSE;
                        break;
                    case IS_NOT_FALSE:
                        scratch.opcode = EEOP_BOOLTEST_IS_NOT_FALSE;
                        break;
                    case IS_UNKNOWN:
                        /* Same as scalar IS NULL test */
                        scratch.opcode = EEOP_NULLTEST_ISNULL;
                        break;
                    case IS_NOT_UNKNOWN:
                        /* Same as scalar IS NOT NULL test */
                        scratch.opcode = EEOP_NULLTEST_ISNOTNULL;
                        break;
                    default:
                        elog(ERROR, "unrecognized booltesttype: %d",
                             (int) btest->booltesttype);
                }

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_CoerceToDomain:
            {
                CoerceToDomain *ctest = (CoerceToDomain *) node;

                ExecInitCoerceToDomain(&scratch, ctest, parent, state,
                                       resv, resnull);
                break;
            }

        case T_CoerceToDomainValue:
            {
                /*
                 * Read from location identified by innermost_domainval.  Note
                 * that innermost_domainval could be NULL, if we're compiling
                 * a standalone domain check rather than one embedded in a
                 * larger expression.  In that case we must read from
                 * econtext->domainValue_datum.  We'll take care of that
                 * scenario at runtime.
                 */
                scratch.opcode = EEOP_DOMAIN_TESTVAL;
                /* we share instruction union variant with case testval */
                scratch.d.casetest.value = state->innermost_domainval;
                scratch.d.casetest.isnull = state->innermost_domainnull;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_CurrentOfExpr:
            {
                scratch.opcode = EEOP_CURRENTOFEXPR;
                ExprEvalPushStep(state, &scratch);
                break;
            }

        case T_NextValueExpr:
            {
                NextValueExpr *nve = (NextValueExpr *) node;

                scratch.opcode = EEOP_NEXTVALUEEXPR;
                scratch.d.nextvalueexpr.seqid = nve->seqid;
                scratch.d.nextvalueexpr.seqtypid = nve->typeId;

                ExprEvalPushStep(state, &scratch);
                break;
            }

        default:
            elog(ERROR, "unrecognized node type: %d",
                 (int) nodeTag(node));
            break;
    }
}

/*
 * Add another expression evaluation step to ExprState->steps.
 *
 * Note that this potentially re-allocates es->steps, therefore no pointer
 * into that array may be used while the expression is still being built.
 */
static void
ExprEvalPushStep(ExprState *es, const ExprEvalStep *s)
{
    if (es->steps_alloc == 0)
    {
        es->steps_alloc = 16;
        es->steps = palloc(sizeof(ExprEvalStep) * es->steps_alloc);
    }
    else if (es->steps_alloc == es->steps_len)
    {
        es->steps_alloc *= 2;
        es->steps = repalloc(es->steps,
                             sizeof(ExprEvalStep) * es->steps_alloc);
    }

    memcpy(&es->steps[es->steps_len++], s, sizeof(ExprEvalStep));
}

/*
 * Perform setup necessary for the evaluation of a function-like expression,
 * appending argument evaluation steps to the steps list in *state, and
 * setting up *scratch so it is ready to be pushed.
 *
 * *scratch is not pushed here, so that callers may override the opcode,
 * which is useful for function-like cases like DISTINCT.
 */
static void
ExecInitFunc(ExprEvalStep *scratch, Expr *node, List *args, Oid funcid,
             Oid inputcollid, PlanState *parent, ExprState *state)
{// #lizard forgives
    int            nargs = list_length(args);
    AclResult    aclresult;
    FmgrInfo   *flinfo;
    FunctionCallInfo fcinfo;
    int            argno;
    ListCell   *lc;

    /* Check permission to call function */
    aclresult = pg_proc_aclcheck(funcid, GetUserId(), ACL_EXECUTE);
    if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, ACL_KIND_PROC, get_func_name(funcid));
    InvokeFunctionExecuteHook(funcid);

    /*
     * Safety check on nargs.  Under normal circumstances this should never
     * fail, as parser should check sooner.  But possibly it might fail if
     * server has been compiled with FUNC_MAX_ARGS smaller than some functions
     * declared in pg_proc?
     */
    if (nargs > FUNC_MAX_ARGS)
        ereport(ERROR,
                (errcode(ERRCODE_TOO_MANY_ARGUMENTS),
                 errmsg_plural("cannot pass more than %d argument to a function",
                               "cannot pass more than %d arguments to a function",
                               FUNC_MAX_ARGS,
                               FUNC_MAX_ARGS)));

    /* Allocate function lookup data and parameter workspace for this call */
    scratch->d.func.finfo = palloc0(sizeof(FmgrInfo));
    scratch->d.func.fcinfo_data = palloc0(sizeof(FunctionCallInfoData));
    flinfo = scratch->d.func.finfo;
    fcinfo = scratch->d.func.fcinfo_data;

    /* Set up the primary fmgr lookup information */
    fmgr_info(funcid, flinfo);
    fmgr_info_set_expr((Node *) node, flinfo);

    /* Initialize function call parameter structure too */
    InitFunctionCallInfoData(*fcinfo, flinfo,
                             nargs, inputcollid, NULL, NULL);

    /* Keep extra copies of this info to save an indirection at runtime */
    scratch->d.func.fn_addr = flinfo->fn_addr;
    scratch->d.func.nargs = nargs;

    /* We only support non-set functions here */
    if (flinfo->fn_retset)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-valued function called in context that cannot accept a set"),
                 parent ? executor_errposition(parent->state,
                                               exprLocation((Node *) node)) : 0));

    /* Build code to evaluate arguments directly into the fcinfo struct */
    argno = 0;
    foreach(lc, args)
    {
        Expr       *arg = (Expr *) lfirst(lc);

        if (IsA(arg, Const))
        {
            /*
             * Don't evaluate const arguments every round; especially
             * interesting for constants in comparisons.
             */
            Const       *con = (Const *) arg;

            fcinfo->arg[argno] = con->constvalue;
            fcinfo->argnull[argno] = con->constisnull;
        }
        else
        {
            ExecInitExprRec(arg, parent, state,
                            &fcinfo->arg[argno], &fcinfo->argnull[argno]);
        }
        argno++;
    }

    /* Insert appropriate opcode depending on strictness and stats level */
    if (pgstat_track_functions <= flinfo->fn_stats)
    {
        if (flinfo->fn_strict && nargs > 0)
            scratch->opcode = EEOP_FUNCEXPR_STRICT;
        else
            scratch->opcode = EEOP_FUNCEXPR;
    }
    else
    {
        if (flinfo->fn_strict && nargs > 0)
            scratch->opcode = EEOP_FUNCEXPR_STRICT_FUSAGE;
        else
            scratch->opcode = EEOP_FUNCEXPR_FUSAGE;
    }
}

/*
 * Add expression steps deforming the ExprState's inner/outer/scan slots
 * as much as required by the expression.
 */
static void
ExecInitExprSlots(ExprState *state, Node *node)
{
    LastAttnumInfo info = {0, 0, 0};
    ExprEvalStep scratch;

    /*
     * Figure out which attributes we're going to need.
     */
    get_last_attnums_walker(node, &info);

    /* Emit steps as needed */
    if (info.last_inner > 0)
    {
        scratch.opcode = EEOP_INNER_FETCHSOME;
        scratch.d.fetch.last_var = info.last_inner;
        ExprEvalPushStep(state, &scratch);
    }
    if (info.last_outer > 0)
    {
        scratch.opcode = EEOP_OUTER_FETCHSOME;
        scratch.d.fetch.last_var = info.last_outer;
        ExprEvalPushStep(state, &scratch);
    }
    if (info.last_scan > 0)
    {
        scratch.opcode = EEOP_SCAN_FETCHSOME;
        scratch.d.fetch.last_var = info.last_scan;
        ExprEvalPushStep(state, &scratch);
    }
}

/*
 * get_last_attnums_walker: expression walker for ExecInitExprSlots
 */
static bool
get_last_attnums_walker(Node *node, LastAttnumInfo *info)
{// #lizard forgives
    if (node == NULL)
        return false;
    if (IsA(node, Var))
    {
        Var           *variable = (Var *) node;
        AttrNumber    attnum = variable->varattno;

        switch (variable->varno)
        {
            case INNER_VAR:
                info->last_inner = Max(info->last_inner, attnum);
                break;

            case OUTER_VAR:
                info->last_outer = Max(info->last_outer, attnum);
                break;

                /* INDEX_VAR is handled by default case */

            default:
                info->last_scan = Max(info->last_scan, attnum);
                break;
        }
        return false;
    }

    /*
     * Don't examine the arguments or filters of Aggrefs or WindowFuncs,
     * because those do not represent expressions to be evaluated within the
     * calling expression's econtext.  GroupingFunc arguments are never
     * evaluated at all.
     */
    if (IsA(node, Aggref))
        return false;
    if (IsA(node, WindowFunc))
        return false;
    if (IsA(node, GroupingFunc))
        return false;
    return expression_tree_walker(node, get_last_attnums_walker,
                                  (void *) info);
}

/*
 * Prepare step for the evaluation of a whole-row variable.
 * The caller still has to push the step.
 */
static void
ExecInitWholeRowVar(ExprEvalStep *scratch, Var *variable, PlanState *parent)
{
    /* fill in all but the target */
    scratch->opcode = EEOP_WHOLEROW;
    scratch->d.wholerow.var = variable;
    scratch->d.wholerow.first = true;
    scratch->d.wholerow.slow = false;
    scratch->d.wholerow.tupdesc = NULL; /* filled at runtime */
    scratch->d.wholerow.junkFilter = NULL;

    /*
     * If the input tuple came from a subquery, it might contain "resjunk"
     * columns (such as GROUP BY or ORDER BY columns), which we don't want to
     * keep in the whole-row result.  We can get rid of such columns by
     * passing the tuple through a JunkFilter --- but to make one, we have to
     * lay our hands on the subquery's targetlist.  Fortunately, there are not
     * very many cases where this can happen, and we can identify all of them
     * by examining our parent PlanState.  We assume this is not an issue in
     * standalone expressions that don't have parent plans.  (Whole-row Vars
     * can occur in such expressions, but they will always be referencing
     * table rows.)
     */
    if (parent)
    {
        PlanState  *subplan = NULL;

        switch (nodeTag(parent))
        {
            case T_SubqueryScanState:
                subplan = ((SubqueryScanState *) parent)->subplan;
                break;
            case T_CteScanState:
                subplan = ((CteScanState *) parent)->cteplanstate;
                break;
            default:
                break;
        }

        if (subplan)
        {
            bool        junk_filter_needed = false;
            ListCell   *tlist;

            /* Detect whether subplan tlist actually has any junk columns */
            foreach(tlist, subplan->plan->targetlist)
            {
                TargetEntry *tle = (TargetEntry *) lfirst(tlist);

                if (tle->resjunk)
                {
                    junk_filter_needed = true;
                    break;
                }
            }

            /* If so, build the junkfilter now */
            if (junk_filter_needed)
            {
                scratch->d.wholerow.junkFilter =
                    ExecInitJunkFilter(subplan->plan->targetlist,
                                       ExecGetResultType(subplan)->tdhasoid,
                                       ExecInitExtraTupleSlot(parent->state));
            }
        }
    }
}

/*
 * Prepare evaluation of an ArrayRef expression.
 */
static void
ExecInitArrayRef(ExprEvalStep *scratch, ArrayRef *aref, PlanState *parent,
                 ExprState *state, Datum *resv, bool *resnull)
{// #lizard forgives
    bool        isAssignment = (aref->refassgnexpr != NULL);
    ArrayRefState *arefstate = palloc0(sizeof(ArrayRefState));
    List       *adjust_jumps = NIL;
    ListCell   *lc;
    int            i;

    /* Fill constant fields of ArrayRefState */
    arefstate->isassignment = isAssignment;
    arefstate->refelemtype = aref->refelemtype;
    arefstate->refattrlength = get_typlen(aref->refarraytype);
    get_typlenbyvalalign(aref->refelemtype,
                         &arefstate->refelemlength,
                         &arefstate->refelembyval,
                         &arefstate->refelemalign);

    /*
     * Evaluate array input.  It's safe to do so into resv/resnull, because we
     * won't use that as target for any of the other subexpressions, and it'll
     * be overwritten by the final EEOP_ARRAYREF_FETCH/ASSIGN step, which is
     * pushed last.
     */
    ExecInitExprRec(aref->refexpr, parent, state, resv, resnull);

    /*
     * If refexpr yields NULL, and it's a fetch, then result is NULL.  We can
     * implement this with just JUMP_IF_NULL, since we evaluated the array
     * into the desired target location.
     */
    if (!isAssignment)
    {
        scratch->opcode = EEOP_JUMP_IF_NULL;
        scratch->d.jump.jumpdone = -1;    /* adjust later */
        ExprEvalPushStep(state, scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
    }

    /* Verify subscript list lengths are within limit */
    if (list_length(aref->refupperindexpr) > MAXDIM)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
                        list_length(aref->refupperindexpr), MAXDIM)));

    if (list_length(aref->reflowerindexpr) > MAXDIM)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
                        list_length(aref->reflowerindexpr), MAXDIM)));

    /* Evaluate upper subscripts */
    i = 0;
    foreach(lc, aref->refupperindexpr)
    {
        Expr       *e = (Expr *) lfirst(lc);

        /* When slicing, individual subscript bounds can be omitted */
        if (!e)
        {
            arefstate->upperprovided[i] = false;
            i++;
            continue;
        }

        arefstate->upperprovided[i] = true;

        /* Each subscript is evaluated into subscriptvalue/subscriptnull */
        ExecInitExprRec(e, parent, state,
                        &arefstate->subscriptvalue, &arefstate->subscriptnull);

        /* ... and then ARRAYREF_SUBSCRIPT saves it into step's workspace */
        scratch->opcode = EEOP_ARRAYREF_SUBSCRIPT;
        scratch->d.arrayref_subscript.state = arefstate;
        scratch->d.arrayref_subscript.off = i;
        scratch->d.arrayref_subscript.isupper = true;
        scratch->d.arrayref_subscript.jumpdone = -1;    /* adjust later */
        ExprEvalPushStep(state, scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
        i++;
    }
    arefstate->numupper = i;

    /* Evaluate lower subscripts similarly */
    i = 0;
    foreach(lc, aref->reflowerindexpr)
    {
        Expr       *e = (Expr *) lfirst(lc);

        /* When slicing, individual subscript bounds can be omitted */
        if (!e)
        {
            arefstate->lowerprovided[i] = false;
            i++;
            continue;
        }

        arefstate->lowerprovided[i] = true;

        /* Each subscript is evaluated into subscriptvalue/subscriptnull */
        ExecInitExprRec(e, parent, state,
                        &arefstate->subscriptvalue, &arefstate->subscriptnull);

        /* ... and then ARRAYREF_SUBSCRIPT saves it into step's workspace */
        scratch->opcode = EEOP_ARRAYREF_SUBSCRIPT;
        scratch->d.arrayref_subscript.state = arefstate;
        scratch->d.arrayref_subscript.off = i;
        scratch->d.arrayref_subscript.isupper = false;
        scratch->d.arrayref_subscript.jumpdone = -1;    /* adjust later */
        ExprEvalPushStep(state, scratch);
        adjust_jumps = lappend_int(adjust_jumps,
                                   state->steps_len - 1);
        i++;
    }
    arefstate->numlower = i;

    /* Should be impossible if parser is sane, but check anyway: */
    if (arefstate->numlower != 0 &&
        arefstate->numupper != arefstate->numlower)
        elog(ERROR, "upper and lower index lists are not same length");

    if (isAssignment)
    {
        Datum       *save_innermost_caseval;
        bool       *save_innermost_casenull;

        /*
         * We might have a nested-assignment situation, in which the
         * refassgnexpr is itself a FieldStore or ArrayRef that needs to
         * obtain and modify the previous value of the array element or slice
         * being replaced.  If so, we have to extract that value from the
         * array and pass it down via the CaseTestExpr mechanism.  It's safe
         * to reuse the CASE mechanism because there cannot be a CASE between
         * here and where the value would be needed, and an array assignment
         * can't be within a CASE either.  (So saving and restoring
         * innermost_caseval is just paranoia, but let's do it anyway.)
         *
         * Since fetching the old element might be a nontrivial expense, do it
         * only if the argument actually needs it.
         */
        if (isAssignmentIndirectionExpr(aref->refassgnexpr))
        {
            scratch->opcode = EEOP_ARRAYREF_OLD;
            scratch->d.arrayref.state = arefstate;
            ExprEvalPushStep(state, scratch);
        }

        /* ARRAYREF_OLD puts extracted value into prevvalue/prevnull */
        save_innermost_caseval = state->innermost_caseval;
        save_innermost_casenull = state->innermost_casenull;
        state->innermost_caseval = &arefstate->prevvalue;
        state->innermost_casenull = &arefstate->prevnull;

        /* evaluate replacement value into replacevalue/replacenull */
        ExecInitExprRec(aref->refassgnexpr, parent, state,
                        &arefstate->replacevalue, &arefstate->replacenull);

        state->innermost_caseval = save_innermost_caseval;
        state->innermost_casenull = save_innermost_casenull;

        /* and perform the assignment */
        scratch->opcode = EEOP_ARRAYREF_ASSIGN;
        scratch->d.arrayref.state = arefstate;
        ExprEvalPushStep(state, scratch);
    }
    else
    {
        /* array fetch is much simpler */
        scratch->opcode = EEOP_ARRAYREF_FETCH;
        scratch->d.arrayref.state = arefstate;
        ExprEvalPushStep(state, scratch);
    }

    /* adjust jump targets */
    foreach(lc, adjust_jumps)
    {
        ExprEvalStep *as = &state->steps[lfirst_int(lc)];

        if (as->opcode == EEOP_ARRAYREF_SUBSCRIPT)
        {
            Assert(as->d.arrayref_subscript.jumpdone == -1);
            as->d.arrayref_subscript.jumpdone = state->steps_len;
        }
        else
        {
            Assert(as->opcode == EEOP_JUMP_IF_NULL);
            Assert(as->d.jump.jumpdone == -1);
            as->d.jump.jumpdone = state->steps_len;
        }
    }
}

/*
 * Helper for preparing ArrayRef expressions for evaluation: is expr a nested
 * FieldStore or ArrayRef that needs the old element value passed down?
 *
 * (We could use this in FieldStore too, but in that case passing the old
 * value is so cheap there's no need.)
 *
 * Note: it might seem that this needs to recurse, but it does not; the
 * CaseTestExpr, if any, will be directly the arg or refexpr of the top-level
 * node.  Nested-assignment situations give rise to expression trees in which
 * each level of assignment has its own CaseTestExpr, and the recursive
 * structure appears within the newvals or refassgnexpr field.
 */
static bool
isAssignmentIndirectionExpr(Expr *expr)
{// #lizard forgives
    if (expr == NULL)
        return false;            /* just paranoia */
    if (IsA(expr, FieldStore))
    {
        FieldStore *fstore = (FieldStore *) expr;

        if (fstore->arg && IsA(fstore->arg, CaseTestExpr))
            return true;
    }
    else if (IsA(expr, ArrayRef))
    {
        ArrayRef   *arrayRef = (ArrayRef *) expr;

        if (arrayRef->refexpr && IsA(arrayRef->refexpr, CaseTestExpr))
            return true;
    }
    return false;
}

/*
 * Prepare evaluation of a CoerceToDomain expression.
 */
static void
ExecInitCoerceToDomain(ExprEvalStep *scratch, CoerceToDomain *ctest,
                       PlanState *parent, ExprState *state,
                       Datum *resv, bool *resnull)
{
    ExprEvalStep scratch2;
    DomainConstraintRef *constraint_ref;
    Datum       *domainval = NULL;
    bool       *domainnull = NULL;
    Datum       *save_innermost_domainval;
    bool       *save_innermost_domainnull;
    ListCell   *l;

    scratch->d.domaincheck.resulttype = ctest->resulttype;
    /* we'll allocate workspace only if needed */
    scratch->d.domaincheck.checkvalue = NULL;
    scratch->d.domaincheck.checknull = NULL;

    /*
     * Evaluate argument - it's fine to directly store it into resv/resnull,
     * if there's constraint failures there'll be errors, otherwise it's what
     * needs to be returned.
     */
    ExecInitExprRec(ctest->arg, parent, state, resv, resnull);

    /*
     * Note: if the argument is of varlena type, it could be a R/W expanded
     * object.  We want to return the R/W pointer as the final result, but we
     * have to pass a R/O pointer as the value to be tested by any functions
     * in check expressions.  We don't bother to emit a MAKE_READONLY step
     * unless there's actually at least one check expression, though.  Until
     * we've tested that, domainval/domainnull are NULL.
     */

    /*
     * Collect the constraints associated with the domain.
     *
     * Note: before PG v10 we'd recheck the set of constraints during each
     * evaluation of the expression.  Now we bake them into the ExprState
     * during executor initialization.  That means we don't need typcache.c to
     * provide compiled exprs.
     */
    constraint_ref = (DomainConstraintRef *)
        palloc(sizeof(DomainConstraintRef));
    InitDomainConstraintRef(ctest->resulttype,
                            constraint_ref,
                            CurrentMemoryContext,
                            false);

    /*
     * Compile code to check each domain constraint.  NOTNULL constraints can
     * just be applied on the resv/resnull value, but for CHECK constraints we
     * need more pushups.
     */
    foreach(l, constraint_ref->constraints)
    {
        DomainConstraintState *con = (DomainConstraintState *) lfirst(l);

        scratch->d.domaincheck.constraintname = con->name;

        switch (con->constrainttype)
        {
            case DOM_CONSTRAINT_NOTNULL:
                scratch->opcode = EEOP_DOMAIN_NOTNULL;
                ExprEvalPushStep(state, scratch);
                break;
            case DOM_CONSTRAINT_CHECK:
                /* Allocate workspace for CHECK output if we didn't yet */
                if (scratch->d.domaincheck.checkvalue == NULL)
                {
                    scratch->d.domaincheck.checkvalue =
                        (Datum *) palloc(sizeof(Datum));
                    scratch->d.domaincheck.checknull =
                        (bool *) palloc(sizeof(bool));
                }

                /*
                 * If first time through, determine where CoerceToDomainValue
                 * nodes should read from.
                 */
                if (domainval == NULL)
                {
                    /*
                     * Since value might be read multiple times, force to R/O
                     * - but only if it could be an expanded datum.
                     */
                    if (get_typlen(ctest->resulttype) == -1)
                    {
                        /* Yes, so make output workspace for MAKE_READONLY */
                        domainval = (Datum *) palloc(sizeof(Datum));
                        domainnull = (bool *) palloc(sizeof(bool));

                        /* Emit MAKE_READONLY */
                        scratch2.opcode = EEOP_MAKE_READONLY;
                        scratch2.resvalue = domainval;
                        scratch2.resnull = domainnull;
                        scratch2.d.make_readonly.value = resv;
                        scratch2.d.make_readonly.isnull = resnull;
                        ExprEvalPushStep(state, &scratch2);
                    }
                    else
                    {
                        /* No, so it's fine to read from resv/resnull */
                        domainval = resv;
                        domainnull = resnull;
                    }
                }

                /*
                 * Set up value to be returned by CoerceToDomainValue nodes.
                 * We must save and restore innermost_domainval/null fields,
                 * in case this node is itself within a check expression for
                 * another domain.
                 */
                save_innermost_domainval = state->innermost_domainval;
                save_innermost_domainnull = state->innermost_domainnull;
                state->innermost_domainval = domainval;
                state->innermost_domainnull = domainnull;

                /* evaluate check expression value */
                ExecInitExprRec(con->check_expr, parent, state,
                                scratch->d.domaincheck.checkvalue,
                                scratch->d.domaincheck.checknull);

                state->innermost_domainval = save_innermost_domainval;
                state->innermost_domainnull = save_innermost_domainnull;

                /* now test result */
                scratch->opcode = EEOP_DOMAIN_CHECK;
                ExprEvalPushStep(state, scratch);

                break;
            default:
                elog(ERROR, "unrecognized constraint type: %d",
                     (int) con->constrainttype);
                break;
        }
    }
}
